LG CHEM battery conductor sizing

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Zee

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Installing an LG CHEM RESU16H Prime battery

Electrical Characteristics
Usable Energy 1) 16 kWh
Battery Capacity 64.1 Ah
Voltage Range 350 to 450 VDC
Absolute Max. Voltage 595 VDC
Max. Current (charging/discharging) 20A @ 350V
Max. Power (charging/discharging) 7 kW
Peak Power 2) (only discharging) 11 kW for 10 sec.
Peak Current (only discharging) 32.8A for 10 sec.

Would I use #10 or #8 wire?
 
That's a serious battery. My inclination would be it's a 20 amp circuit and go with a ten. But the rules for pv and battery systems are not something I am real familiar with.

I did not even realize they ran at such a high voltage.
 
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retirede said:
That sounds like a battery out of a plug in hybrid electric vehicle (PHEV).
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I think those voltages are typical of the line side of the inverter. IIRC, the Powerwall has an integrated inverter, but I don't know about the LG product.
 
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gadfly56 said:
I think those voltages are typical of the line side of the inverter. IIRC, the Powerwall has an integrated inverter, but I don't know about the LG product.
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Could be. My daughter has a Pacifica PHEV and its battery is 360V, 16 KwH, made by LG Chem…. which is the basis of my comment.
 
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The logical choices would be to size the conductors for the nominal ampacity corrected for continuous current, so 25A, or for the peak of 33A. A #10 would be good for either with no other derates. If voltage drop were an issue then the #8 would be a good choice.
 
So you are saying if it's a 10 second peak rating then no 125% continuous use factor need be applied? Makes sense!

However ........the peak rating is over 30A (33A), so I think #8 minimum required. #10 is allowable for 30A max. So not OK for 33A.
 
Zee said:
So you are saying if it's a 10 second peak rating then no 125% continuous use factor need be applied? Makes sense!

However ........the peak rating is over 30A (33A), so I think #8 minimum required. #10 is allowable for 30A max. So not OK for 33A.
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I guess if you used 60C rated #10. Being in PV I just assume we are all talking about 90C rated #10. If you are referring to the 240.4(D) OCPD requirements for small conductors, that's an OCPD requirement and not a restriction on the ampacity of the #10. A 90C #10 is rated for 40A in table 310.15(B)(16), if you have an OCPD in the circuit it has to be limited to 30A.
 
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#10 is the spec from LG/SolarEge on the 9.8 kWh unit. I would expect it be the same here. In fact I think the BATT terminals inside the DC connection unit of the inverter can only take a max #10.
 
BandGap1.1eV said:
In fact I think the BATT terminals inside the DC connection unit of the inverter can only take a max #10.
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FWIW, the RESU16H Prime installation manual says on PDF page 15 that the power terminal bocks are rated for "Cable type: 4~10mm² (10~12
AWG)" Which is a little odd, as a random online calculator tells me #8 AWG is 8.6 mm^2, so they would presumably fit fine.

Cheers, Wayne
 
Terminal size has been a problem for LG Chem and Solaredge. For the Resu10H if you were connecting two of them to one inverter you paralleled the batteries. That called for a either a battery combiner with DC 600V OCPDs, or a higher wire size for the combined current. (Code does not really explicitly address it, but interpreting it to be similar to PV strings that makes sense.) Obviously bigger wire is the better option. But the equipment terminals did not support a bigger wire size. Both LG chem and Solaredge, iirc. I've stopped working with them so I don't know if it's changed but in both cases I believe the product designers are in other countries and may not really understand NEC requirements.
 
wwhitney said:
FWIW, the RESU16H Prime installation manual says on PDF page 15 that the power terminal bocks are rated for "Cable type: 4~10mm² (10~12
AWG)" Which is a little odd, as a random online calculator tells me #8 AWG is 8.6 mm^2, so they would presumably fit fine.

Cheers, Wayne
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or maybe UL refused to list them for anything other than #10-#12.
 
jaggedben said:
Terminal size has been a problem for LG Chem and Solaredge. For the Resu10H if you were connecting two of them to one inverter you paralleled the batteries. That called for a either a battery combiner with DC 600V OCPDs, or a higher wire size for the combined current. (Code does not really explicitly address it, but interpreting it to be similar to PV strings that makes sense.) Obviously bigger wire is the better option. But the equipment terminals did not support a bigger wire size. Both LG chem and Solaredge, iirc. I've stopped working with them so I don't know if it's changed but in both cases I believe the product designers are in other countries and may not really understand NEC requirements.
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I tried to stuff a #8 in there and it wasn't happening.

The batteries have an internal 5 kW DC-DC converter that theorhetically limits discharge current and the BMS inside the inverter will not discharge both at once. The installation manual shows a less than helpful wiring detail for when paralleling batteries; just a generic splice somewhere in the line with a single set of #10 back to the inverter. Very counter intuitive.
 
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